Aminoacyl Transfer Rate Dictates Choice of Editing Pathway in Threonyl-tRNA Synthetase

• Published in: The Journal of biological chemistry Vol. 285; no. 31; pp. 23810 - 23817
• Main Authors: Minajigi, Anand, Francklyn, Christopher S.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 30.07.2010; American Society for Biochemistry and Molecular Biology
• Subjects: Adenosine Triphosphate - chemistry; Amino Acid; Amino Acid Editing; Aminoacyl tRNA Synthesis; Aminoacyl tRNA Synthetase; Binding Sites; Catalytic Domain; Escherichia coli; Escherichia coli - enzymology; Fidelity; Hydrolysis; Kinetics; Models, Biological; Models, Chemical; Models, Genetic; Protein Synthesis and Degradation; RNA; RNA Editing; RNA, Transfer, Amino Acyl - chemistry; RNA-Protein Interaction; Serine - chemistry; Solvents - chemistry; Threonine; Threonine - chemistry; Transfer RNA (tRNA); Aminoacyl tRNA Synthetase; Fidelity; Amino Acid; RNA-Protein Interaction; Threonine; Amino Acid Editing; Aminoacyl tRNA Synthesis; Transfer RNA (tRNA)
• ISSN: 0021-9258; 1083-351X; 1083-351X
• DOI: 10.1074/jbc.M110.105320

Aminoacyl-tRNA synthetases hydrolyze aminoacyl adenylates and aminoacyl-tRNAs formed from near-cognate amino acids, thereby increasing translational fidelity. The contributions of pre- and post-transfer editing pathways to the fidelity of Escherichia coli threonyl-tRNA synthetase (ThrRS) were investigated by rapid kinetics. In the pre-steady state, asymmetric activation of cognate threonine and noncognate serine was observed in the active sites of dimeric ThrRS, with similar rates of activation. In the absence of tRNA, seryl-adenylate was hydrolyzed 29-fold faster by the ThrRS catalytic domain than threonyl-adenylate. The rate of seryl transfer to cognate tRNA was only 2-fold slower than threonine. Experiments comparing the rate of ATP consumption to the rate of aminoacyl-tRNAAA formation demonstrated that pre-transfer hydrolysis contributes to proofreading only when the rate of transfer is slowed significantly. Thus, the relative contributions of pre- and post-transfer editing in ThrRS are subject to modulation by the rate of aminoacyl transfer.